1. Field of the Disclosure
The present invention relates to devices and methods for evaporating fluids from an open fluid reservoir, which in some applications may be used to accelerate the rate of concentration of suspended solids therein with or without the feature of promoting or maintaining aerobic conditions within the open fluid reservoir.
2. Background Art
Water and other fluids often accumulate various contaminants, and it is often desirable or necessary to separate the fluid from the contaminant to meet various purity targets or reduce the volume of liquid within an open reservoir, which may be necessary for practical, legal, or other reasons. Such contaminants may include, for example, salts, sulfur, heavy metals, suspended soils, human or animal waste, oils, fertilizers, pharmaceuticals, acid and any other undesirable matter as would be apparent to a person of skill in the art. The sources for contaminated fluids, also called effluent, are many, such as acid mine runoff, petrochemical processing fluids, agricultural runoff, municipal waste water and storm water runoff, and industrial process effluent, to name just a few examples. Frequently, the fluid to be treated is water, although clearly other fluids may need to have contaminants separated therefrom. For the purposes of this application, however, the exact fluid, contaminant, and source of contaminant is not particularly relevant, and so the terms water and contaminant will be used generically to include any fluid and matter, respectively, that one would desire to treat or purify, unless otherwise clearly indicated.
Outdoor open fluid reservoirs, such as retention ponds, aeration reservoirs, dry ponds, open-topped tanks, and the like, are often used to temporarily store effluent that contains undesirable levels of contaminants until the effluent can be treated to separate the contaminant from the water. After separation, the cleaned water can be released to the environment or otherwise used as desired, and the contaminant and/or concentrated effluent can be further processed, recycled, transported to an appropriate landfill, or otherwise disposed of.
When the contaminant is not a volatile substance, one commonly used method of separating the contaminant from the water is to evaporate the water from the effluent, thereby releasing clean water into the atmosphere in the gaseous state in the form of vapor while the contaminant is retained and/or re-captured in the reservoir. Depending on the circulation of effluent into the reservoir, after some period of time the water is either completely evaporated, thereby leaving the contaminants remaining in the reservoir for easy collection and disposal, or the concentration of contaminant is elevated to a point, such as saturation, where it becomes economically advantageous to further process and/or separate the highly concentrated effluent in other ways.
Although the water evaporates naturally at the surface of a pond or other outdoor reservoir, it is often desirable to increase the rate of evaporation to decrease the processing time of the effluent in order to increase economic efficiencies. Thus, it is common to place a reservoir evaporator system directly in the reservoir that effectively accelerates evaporation of the water to the surrounding environment by, for example, increasing the surface area to volume ratio of the effluent to the surrounding air. There are many ways to accomplish this, and of course, the efficacy of this evaporative treatment method is highly dependent on many variables other than the evaporator system, including flow rate of effluent into or through the reservoir, humidity levels of the surrounding environment, the fluid to be evaporated, and temperature, to name a few.
One known type of reservoir evaporator system uses nozzles to spray a fine mist of droplets of the effluent up into the air above the top surface of the reservoir. Under ideal conditions, the water in the droplets evaporates into the surrounding atmosphere more quickly than from the top surface because of the increased surface area to volume ratio, and the contaminants and any un-evaporated droplets fall back into the reservoir. An exemplary reservoir evaporation system generally incorporating this design is disclosed in U.S. Patent Application Publication No. 2010/0139871 to Rasmussen et al. A problem with these misting-types of reservoir evaporation systems, however, is that under non-ideal conditions the contaminates and un-evaporated droplets may be borne by winds away from the reservoir and settle out at nearby areas rather than in the reservoir. This could lead to unwanted deposition of the contaminates in surrounding areas, such as residential or other built-up areas, or uncontrolled release of the contaminates into surrounding environments, all of which are forms of multi-media pollution. Additionally, such systems frequently require a supply of high pressure to force the effluent through a nozzle and adequately aerosolize the effluent into the surrounding air.
Another known type of reservoir evaporator system floats on the top surface of the reservoir and includes a spinning agitator for scooping effluent from the top surface and sprinkling it into the air. The agitator is connected to a source of high pressure air that spins the agitator by means of thrust nozzles, and the exhaust from the thrust nozzles may be directed to further impact the effluent sprinkled into the air to further accelerate evaporation. An exemplary reservoir evaporation generally incorporating this design is disclosed in U.S. Pat. No. 4,001,077 to Kemper. In addition to the potential of causing multi-media pollution, another drawback to these systems is the need to use moving parts, which can frequently break or become jammed through buildup of scale from the contaminants.
Additionally, the inclusion of a high pressure air or liquid supply in each of these reservoir evaporator systems can increase complexity, cost, and maintenance requirements.
A further known type of reservoir evaporator system that dispenses with the use of high pressure air exposes evaporation surfaces that have been wetted with the effluent to the air and wind. One exemplary reservoir evaporation system generally incorporating this design is disclosed in U.S. Pat. No. 7,166,188 to Kadem et al. These designs, while overcoming the problem of drift to surrounding areas, may often require extensive maintenance to keep the evaporation surfaces free of contaminant buildup and often require complex mechanical and/or effluent transfer systems for dispersing the effluent onto the evaporation surfaces.
In view of this existing state of the art, the inventors of the present application have developed a reservoir evaporation system that overcomes in various aspects many of the drawbacks associated with the current systems.